Exclude power analysis notebook from CI (>600s timeout)

06_power_analysis.ipynb runs SyntheticDiD simulate_power which is a
Monte Carlo simulation too slow for pure-Python CI without the Rust
backend. Same category as the already-excluded TROP notebook.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: igerber

.github/workflows/notebooks.yml

@@ -46,11 +46,13 @@ jobs:
         run: |
           pytest --nbmake docs/tutorials/ \
             --nbmake-timeout=600 \
+            --ignore=docs/tutorials/06_power_analysis.ipynb \
             --ignore=docs/tutorials/10_trop.ipynb \
             -v \
             --tb=short
-          # Excluded notebooks:
-          #   10_trop — LOOCV grid search too slow for pure-Python CI (>600s)
+          # Excluded notebooks (too slow for pure-Python CI without Rust backend):
+          #   06_power_analysis — SyntheticDiD simulate_power Monte Carlo (>600s)
+          #   10_trop — LOOCV grid search (>600s)
 
       - name: Upload failed notebook outputs
         if: failure()